📚 Year 12 WJEC Physics: Essential Glossary & Quick Memorization Guide | Year 12 WJEC 物理：词汇术语速记指南
Mastering the terminology of Year 12 WJEC Physics is the first step towards exam success. This guide breaks down the most critical terms across mechanics, materials, waves, electricity and quantum phenomena, pairing clear definitions with memory aids and Chinese translations to help bilingual learners internalise concepts fast.
掌握 Year 12 WJEC 物理术语是考试成功的第一步。本指南分解了力学、材料、波、电学和量子现象中最关键的术语，将清晰的定义与记忆技巧及中文翻译配对，帮助双语学习者快速内化概念。
1. Mechanics & Kinematics | 力学与运动学
Displacement (s) – a vector quantity that measures the shortest straight-line distance from the start point to the finish point in a given direction. It can be zero even if the object has travelled a long path. Mnemonic: displacement = directed length.
位移 (s) – 一个矢量，度量从起点到终点的直线距离及方向。即使物体运动路径很长，位移也可以为零。记法：位移 = 有向长度。
Velocity (v) – the rate of change of displacement; a vector. v = Δs / Δt. If direction changes, velocity changes even when speed is constant. Remember: velocity is speed in a particular direction.
速度 (v) – 位移的变化率；矢量。 v = Δs / Δt。如果方向改变，即使速率恒定，速度仍然会改变。记住：速度是带有方向的速率。
Acceleration (a) – the rate of change of velocity; a vector. a = Δv / Δt. Negative acceleration (deceleration) means the velocity is decreasing in the chosen positive direction. Uniform acceleration gives the famous ‘SUVAT’ equations.
加速度 (a) – 速度的变化率；矢量。 a = Δv / Δt。负加速度（减速）意味着在所取正方向上速度在减小。匀加速情况可用著名的 SUVAT 方程。
SUVAT equations – a set of four kinematic equations linking s, u, v, a and t. Example: v = u + at and s = ut + ½at². They only work when acceleration is constant and motion is in a straight line.
SUVAT 方程 – 关联 s, u, v, a, t 的四个运动学方程。例如：v = u + at 和 s = ut + ½at²。仅当加速度恒定且物体做直线运动时适用。
2. Forces & Newton’s Laws | 力与牛顿定律
Weight (W) – the gravitational force on an object; a vector. W = mg, where g ≈ 9.81 m s⁻² on Earth. Weight is not the same as mass; mass is a scalar and is measured in kg. Tip: Weight depends on the gravitational field strength.
重力 (W) – 作用在物体上的引力；矢量。 W = mg，地球上 g ≈ 9.81 m s⁻²。重力和质量不同；质量是标量，单位是千克。提示：重力取决于重力场强度。
Newton’s Second Law – the resultant force on an object equals the rate of change of its momentum. For constant mass: F = ma. This is a vector equation: the acceleration is in the direction of the net force.
牛顿第二定律 – 物体所受合力等于其动量的变化率。质量不变时：F = ma。这是一个矢量方程：加速度方向与合力方向相同。
Newton’s Third Law – if body A exerts a force on body B, body B exerts an equal and opposite force on body A. These forces act on different bodies, so they never cancel. Remember: action and reaction are paired but act on different objects.
牛顿第三定律 – 若物体 A 对物体 B 施加一个力，则 B 同时对 A 施加大小相等、方向相反的力。这两个力作用在不同物体上，不会互相抵消。记住：作用力与反作用力成对出现但作用在不同物体上。
Free-body diagram – a sketch showing all the forces acting on a single object. Use it to resolve forces and find the resultant. Always draw force arrows pulling away from the centre of mass.
受力分析图 – 表示作用在单个物体上所有力的草图。用它来分解力并求合力。力箭头总是从质心向外拉。
3. Energy, Work & Power | 能量、功与功率
Work done (W) – the energy transferred by a force. W = F s cos θ, where θ is the angle between the force and the displacement. If the force is perpendicular to displacement (θ = 90°), no work is done. Unit: joule (J).
功 (W) – 力传递的能量。 W = F s cos θ，θ 是力与位移间的夹角。若力垂直于位移 (θ = 90°)，则不做功。单位：焦耳 (J)。
Kinetic energy (Eₖ) – the energy of an object due to its motion. Eₖ = ½ m v². Doubling speed quadruples kinetic energy. This is a scalar quantity.
动能 (Eₖ) – 物体因运动而具有的能量。 Eₖ = ½ m v²。速度加倍，动能变为四倍。动能为标量。
Gravitational potential energy (Eₚ) – energy stored in an object because of its position in a gravitational field. Near Earth’s surface: Eₚ = m g h. The ‘height’ h must be measured from a chosen zero level.
重力势能 (Eₚ) – 物体因在重力场中的位置而储存的能量。近地表：Eₚ = m g h。高度 h 需从选定的零势能面量起。
Power (P) – the rate of doing work. P = W / t = F v (for constant force and velocity). Unit: watt (W). Think: power tells you how fast energy is transferred.
功率 (P) – 做功的快慢。 P = W / t = F v（力与速度恒定时）。单位：瓦特 (W)。思路：功率表示能量转化的速率。
Conservation of energy – energy cannot be created or destroyed, only transferred or converted from one form to another. In a closed system, total energy remains constant. Treat calculations by tracking energy types before and after.
能量守恒 – 能量既不能凭空产生也不能凭空消失，只能从一种形式转化为另一种形式。在孤立系统中，总能量保持不变。计算时追踪转化前后的能量形式即可。
4. Materials & Hooke’s Law | 材料与胡克定律
Hooke’s Law – the extension of a spring is directly proportional to the applied force, provided the elastic limit is not exceeded. F = k x, where k is the spring constant (N m⁻¹). The minus sign in F = −k x shows the restoring force opposes extension.
胡克定律 – 不超过弹性限度时，弹簧的伸长量与所受外力成正比。 F = k x，k 为劲度系数 (N m⁻¹)。F = −k x 中的负号表示恢复力与伸长方向相反。
Spring constant (k) – a measure of a spring’s stiffness. A larger k means a stiffer spring. Determined from the gradient of a force–extension graph up to the limit of proportionality.
劲度系数 (k) – 衡量弹簧软硬程度的量。k 越大，弹簧越硬。可由力-伸长图在比例极限内的斜率求出。
Elastic limit – the maximum force (or stress) that can be applied to a material so that it returns to its original shape when the force is removed. Beyond this, plastic deformation occurs.
弹性限度 – 撤去外力后材料能恢复原状的最大应力。超过该限度将发生塑性形变。
Stress & strain – stress σ = F / A (unit Pa), strain ε = ΔL / L (no unit). Young modulus E = stress / strain = (F L) / (A ΔL). Stress measures how much load is applied per area; strain measures fractional extension.
应力与应变 – 应力 σ = F / A (单位 Pa)，应变 ε = ΔL / L (无单位)。杨氏模量 E = 应力/应变 = (F L) / (A ΔL)。应力衡量单位面积上的载荷，应变衡量相对伸长量。
5. Waves: Properties & Types | 波的性质与类型
Transverse wave – oscillation is perpendicular to the direction of energy transfer. Examples: light, water ripples, waves on a string. Use a slinky waved side-to-side to visualise.
横波 – 振动方向与能量传播方向垂直。例如：光、水波、绳波。可想象左右抖动一个弹簧来理解。
Longitudinal wave – oscillation is parallel to the direction of energy transfer. Examples: sound, ultrasound, P-waves. These waves show compressions and rarefactions.
纵波 – 振动方向与能量传播方向平行。例如：声音、超声波、P波。表现出疏部和密部。
Frequency (f) & period (T) – frequency is the number of complete oscillations per second (Hz). T = 1 / f. The wave equation: v = f λ, where λ is wavelength (m) and v is wave speed (m s⁻¹).
频率 (f) 与周期 (T) – 频率是每秒完整振动的次数 (Hz)。 T = 1 / f。波速方程：v = f λ，其中 λ 是波长 (m)，v 是波速 (m s⁻¹)。
Amplitude (A) – the maximum displacement from the equilibrium position. In a sound wave, larger amplitude means louder sound. Intensity is proportional to amplitude squared.
振幅 (A) – 离开平衡位置的最大位移。声波中振幅越大，声音越响。强度与振幅的平方成正比。
6. Superposition & Interference | 叠加与干涉
Principle of superposition – when two or more waves meet at a point, the resultant displacement is the vector sum of the individual displacements. This happens without the waves being permanently changed.
叠加原理 – 当两列或多列波在某点相遇时，合位移等于各列波单独引起的位移的矢量和。相遇后波仍按原样继续传播。
Constructive interference – occurs when waves meet in phase (path difference = n λ, n = 0, 1, 2…). Amplitudes add, producing a wave of larger amplitude. The resulting displacement is a maximum.
相长干涉 – 波相遇时相位相同（波程差 = n λ，n = 0, 1, 2…），振幅相加，产生振幅更大的波。合位移为极大值。
Destructive interference – occurs when waves meet completely out of phase (path difference = (n + ½) λ). Amplitudes subtract; if amplitudes are equal, total cancellation gives zero displacement.
相消干涉 – 波相遇时反相（波程差 = (n + ½) λ），振幅相减；若振幅相等则完全抵消，合位移为零。
Coherence – two wave sources are coherent if they have a constant phase difference and the same frequency. Lasers give coherent light; for Young’s double-slit, use a single slit before the two slits to ensure coherence.
相干性 – 两个波源频率相同且相位差恒定时称为相干波源。激光提供相干光；杨氏双缝实验中，在双缝前加一单缝可保证相干性。
7. Optics: Refraction & Lenses | 光学：折射与透镜
Refractive index (n) – a measure of how much a medium slows down light. n = c / v, where c is the speed of light in a vacuum. A higher n means light bends more towards the normal when entering the medium.
折射率 (n) – 衡量介质对光速减慢程度的量。 n = c / v，c 为真空中光速。n 越大，光进入该介质时向法线偏折越多。
Snell’s Law – n₁ sin θ₁ = n₂ sin θ₂, where θ₁ is the angle of incidence and θ₂ is the angle of refraction. It can be used to calculate the critical angle when the second medium is less dense.
斯涅尔定律 – n₁ sin θ₁ = n₂ sin θ₂，θ₁ 为入射角，θ₂ 为折射角。当光从光密介质到光疏介质时可用它计算临界角。
Critical angle (θ_c) – the angle of incidence in the denser medium for which the angle of refraction is 90°. sin θ_c = n₂ / n₁ (n₁ > n₂). For angles greater than θ_c, total internal reflection occurs.
临界角 (θ_c) – 光密介质中折射角为 90° 时的入射角。 sin θ_c = n₂ / n₁ (n₁ > n₂)。入射角大于临界角时发生全内反射。
Converging (convex) lens – brings parallel rays to a focus. Real image: inverted, can be projected; virtual image: upright, seen through the lens. The lens formula: 1/f = 1/u + 1/v.
会聚透镜（凸透镜） – 使平行光会聚于焦点。实像：倒立、可投射；虚像：正立、通过透镜观察。透镜公式：1/f = 1/u + 1/v。
8. Electricity: Current, Voltage & Resistance | 电流、电压与电阻
Electric current (I) – rate of flow of charge. I = ΔQ / Δt, unit: ampere (A). In metallic conductors, current is due to movement of free electrons. Conventional current flows from positive to negative.
电流 (I) – 电荷的流动速率。 I = ΔQ / Δt，单位：安培 (A)。金属导体中电流由自由电子移动形成。约定电流方向从正到负。
Potential difference (V) – energy transferred per unit charge between two points. V = W / Q, unit: volt (V). Often thought of as the ‘push’ driving electrons around a circuit; it is measured across a component.
电势差 (V) – 两点间单位电荷转移的能量。 V = W / Q，单位：伏特 (V)。常被看作驱动电子在电路中运动的“推力”；跨元件测量。
Resistance (R) – opposition to current flow. R = V / I, unit: ohm (Ω). For an ohmic conductor, V ∝ I at constant temperature. Resistivity ρ links resistance to dimensions: R = ρ L / A.
电阻 (R) – 对电流的阻碍作用。 R = V / I，单位：欧姆 (Ω)。对欧姆导体，温度不变时 V ∝ I。电阻率 ρ 将电阻与尺寸关联： R = ρ L / A。
Ohm’s Law – for a metallic conductor at constant temperature, the current through it is directly proportional to the potential difference across it. Not all components obey Ohm’s Law (e.g., diode, filament lamp).
欧姆定律 – 对温度不变的金属导体，通过它的电流与两端电压成正比。并非所有元件都遵循欧姆定律（如二极管、灯丝灯泡）。
9. DC Circuits & Potential Dividers | 直流电路与分压器
Kirchhoff’s First Law – the sum of currents entering a junction equals the sum of currents leaving it. This is a consequence of charge conservation. Use it to find missing currents in parallel branches.
基尔霍夫第一定律 – 流入节点的电流总和等于流出节点的电流总和。这是电荷守恒的结果。用于求并联支路的未知电流。
Kirchhoff’s Second Law – in any closed loop, the sum of e.m.f.s equals the sum of potential differences (p.d.s). This follows from energy conservation. Apply it to loops in series-parallel circuits with more than one cell.
基尔霍夫第二定律 – 任一闭合回路中，电动势的总和等于各段电压降的总和。源于能量守恒。用于含有多个电池的串并联电路回路分析。
Potential divider – two resistors in series split the supply voltage: V_out = V_in × (R₂ / (R₁ + R₂)). The output voltage is a fraction of the input, adjustable via a variable resistor. Widely used in sensor circuits.
分压器 – 两个电阻串联可分割电源电压：V_out = V_in × (R₂ / (R₁ + R₂))。输出电压是输入电压的一部分，通过可变电阻调节。广泛用于传感器电路。
Electromotive force (e.m.f., ε) – the energy supplied per unit charge by a source, measured in volts. Internal resistance (r) causes terminal p.d. to drop when current flows: V = ε − I r.
电动势 (e.m.f., ε) – 电源对每单位电荷提供的能量，单位伏特。内阻 (r) 导致有电流时路端电压下降： V = ε − I r。
10. Quantum Phenomena: Photons & Spectra | 量子现象：光子与光谱
Photon – a quantum (packet) of electromagnetic energy. Energy E = h f = h c / λ, where h is Planck’s constant (6.63 × 10⁻³⁴ J s). The photon model explains the photoelectric effect.
光子 – 电磁辐射的量子（能量包）。能量 E = h f = h c / λ，h 为普朗克常数 (6.63 × 10⁻³⁴ J s)。光子模型可解释光电效应。
Photoelectric effect – emission of electrons from a metal surface when light of frequency above the threshold frequency f₀ shines on it. Key observations: instantaneous emission, independent of intensity, and kinetic energy depends on frequency (Eₖ_max = h f − φ).
光电效应 – 用频率高于截止频率 f₀ 的光照射金属表面时发射电子的现象。关键特征：瞬间发射、与光强无关、最大动能取决于频率 (Eₖ_max = h f − φ)。
Work function (φ) – the minimum energy needed to remove an electron from the metal surface. φ = h f₀. Photon energy below φ yields no emission regardless of intensity.
逸出功 (φ) – 从金属表面移去一个电子所需的最小能量。 φ = h f₀。光子能量低于 φ 时，无论光强多大都不会发射电子。
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